Acute gut mucosal injury occurs commonly in various critical surgical disorders such as trauma, thermal injury, shock, sepsis, and massive surgical operations. Since the exact mechanisms underlying mucosal injury and repair are still obscure, effective therapies to preserve the epithelial integrity in patients with critical surgical illnesss are limited, contributing to mucosal hemorrhage, delayed healing, epithelial barrier dysfunction, and the translocation of luminal toxic substances and bacteria to the blood stream. During previous funding period, we have demonstrated that activation of Wnt signaling stimulates mucosal healing after acute injury and also identified a novel mechanism through which the RNA-binding proteins HuR and AUF1 regulate expression of c-Myc and JunD in critical surgical conditions. Recently, the essential contribution of posttranscriptional events, particularly altere mRNA turnover and translation through microRNAs (miRNAs), in the control of gene expression program in the mucosal tissues is becoming increasingly recognized, but little is known about their importance in the control of mucosal injury/repair in critical surgical conditions. Based on our significant progress during the previous funding period and exciting preliminary studies, experiments proposed in this competitive renewal application are to test the HYPOTHESIS that miRNA-222 (miR-222) and miR-503 play an important role in the regulation of mucosal healing after acute injury in critical surgical conditions by altering the stability and/or translation of arget mRNAs. Three specific aims are proposed to test the hypothesis. 1) To define the exact roles of miR-222 and miR-503 in mucosal healing after acute injury in critical surgical conditions. 2) To determine if miR-222 and miR-503 regulate mucosal healing by altering the stability and translation of their target mRNAs. 3) To characterize the exact mechanism by which miR-222 and miR-503 regulate expression of key molecules of Wnt signals under surgical stress. Completion of these specific aims will make a significant conceptual advance by linking the miRNA- mediated posttranscriptional regulation with mucosal healing in patients with critical surgical illness and will create a fundamental base for development of novel therapies to preserve the epithelial integrity. Moreover, the identification of the mRNA targets that mediate the actions of miRNAs in mucosal healing will also reveal previously unrecognized components of cellular stress responses that may serve as targets for more traditional drug development.